Is the 6502 still alive? Are people still using them? My question
is from a hobby perspective. I am experimenting with little micro-
and embedded systems and the 6502 looks like a good candidate to
play with because of its simplicity.

A Gimix Ghost, 12 serial ports (7 users, 2 printers, 1 modem), 20M
drive and 512K of RAM. We'd compile, edit print and send out stories
on that machine. This was before the IBM PC! I still don't undertand
why the used the terminal port DB25 for the Parallel printer and the
modem port DB25 for the RS232 port. Couldn't they just follow the
existing standard! ;-) And for those of you with no sense of humor
there was no standard. But IBM did seem to setup their equipment
different to the way everyone else, at the time, that I can remember.

6809 was the best 8-bit CPU ever made.
As for OS-9, I vaguely remember a Byte column (1986?) where Jerry Pournelle
said OS-9 compared to DOS like Robert de Niro compared to Sylvester
Stallone. (Was Roman-Digit-Sylvester that bad?)

Aaargh! I was afraid someone would say this.
The enhancements don't change the architecture, and the technology (CMOS
instead of NMOS) even less so. The design is pure Motorola, so that's where
the kudos goes.

I seem to recall that the 6309 had a few more instructions and some
other extras either by setting a bit or something. Memory it the first
thing .... oh I forget. ;-)

I love the 6809, it was the first assembly language that looked like
C (dare I call it high level?). Then I got hit with the 68000 which I
hated (more because of all the extra support chips than anything
else).

They most certainly do! They add new registers and new addressing
modes. If it wasn't a new architecture, you'd be able to execute HD6309
code on a 6809, which you usually can't. The DEFINITION of computer
architecture (as established by Gerrit Blauuw and Fred Brooks in the
early 1960s) is the programmer-visible characteristics of the system.
The 6809 and HD6309 definitely does NOT have an identical set of
programmer-visibile characteristics.

True. In the Blauuw and Brooks taxonomy, that would be a matter
of "realization" (if the architecture and logic-level implementation
were otherwise identical).

The base design is by Motorola, but if you're trying to give them
exclusive credit for the HD6309 design I would say you're way off base.
The Hitachi designers did a non trivial amount of work extending the
architecture.

As they did in extending the Z80 to the 64180, which they sold
back to Zilog later and became the Z180. If that had existed in
1979 the 8086/8 architecture and the IBM PC would probably never
have surfaced, since the 64180 could handle 1 Meg of memory. Not
as conveniently as the 8086 architecture, though.

--
Some similarities between GWB and Mussolini:
a) The strut; b) Making war until brought up short:

Well, looks like we have different ideas of the term "architecture". My
definition is something like "The basic design of a system. How the
components work together." In GB&FB's definition (not DEFINITION; there's no
need to shout) two architectures can only be the same if the two products
are the same. Would this also hold for the original meaning of architecture;
that two buildings have the same architecture if they are exact copies?
IIRC (CMIIW) the 6309 was backward object code compatible with and a
pin-for-pin replacement for the 6809. How much closer can you get without
being identical?

And your credentials justifying your definition being more authoritative
(or even just more appropriate to daily use) than that of Blauuw and
Brooks would be...?

Even if we were to accept your criterion "how the components work
together", the MC6809 and HD6309 would have distinct architectures, as
the HD6309 has some components that are not present at all in the
MC6809. The HD6309 components, therefore, must "work together" at least
somewhat differently than those of the MC6809.

False. For example, Blaauw and Brooks consider the IBM 709 and IBM 7090
to have the same architecture. Yet the realization is much different;
the 709 was built from tubes, and the 7090 from transistors. Perhaps
more to the point, the IBM System/360 Model 40 and Model 65 have the
same architecture, and are realized with the same family of MST circuits,
yet their implementation (logic design) is almost entirely different.

Irrelevant; the word has a different meaning when applied to computers,
and Blaauw and Brooks defined it in that context. A sensible person
wouldn't try to describe the architecture of a computer using terms
applicable to the architecture of a building. One doesn't hear about
computers being of Greek, Neo-Classical, or Art Deco architectural
styles. The use of the word "architecture" for computers is obviously
by analogy, but one shouldn't try to push analogies too far.

Some people now use the word architecture to refer to the internal
implementation details of the processor, such as how many pipeline
stages are present and what microoperations a macrooperation is
decomposed into; that is more properly termed "microarchitecture".

The IBM System/370 was essentially a superset of the System/360, yet
the architects considered it to be a distinct architecture, because
System/370 program would not necessarily run on a System/360. The
HD6309 extends the MC6809 to an even greater extent than the System/370
extended the System/360.

If rather than claiming that the HD6309 and MC6809 share the same
architecture, you instead claimed that the HD6309 architecture is an
extension of the MC6809 architecture, I'd have no objection.

Or if you wanted to say that the MC6809 and HD6309 share the same
"architectural style", I wouldn't argue. As far as I know, there has
never been any effort to formalize a definition of architectural style
as applied to computers. Would the MC6801 share that architectural
style? What about the PDP-11? Hard to say. There are obvious
similarities, but also significant differences.

There's still a few newer products high volume products based on the core.
Western Design Center owns some IP on the 6502 and sells it. I worked for a
short time on a Seiko message watch, a few years back, based on the 6502 core.

Hmmm. The last time I worked with this family was about 20 years ago.
Personally I wouldn't go back because it requires too much infrastructure
to get started. By the time you've added address decoding, non volatile
and volatile memory, and peripherals, you've gotten yourself up to an
outdated arhitecture with limited capabilities.

There's nothing simple about it.

If you want simple, get started with a single chip microcontroller
solution. Any of the current crop of flash based microcontroller
offerings (PIC, AVR, MSP430, Zilog Z8 and the like) will run rings
around the 6502, and carries all the stuff I listed above all onboard.

And when you start looking at those, make sure you look at current parts.
You'll find web sites will trend to older equipment. For example in
the PIC world if you start Googling you'll see the 16F84 as the gold
standard. It was: 8 years ago. Now there are a heaping helping of
newer faster, better cheaper parts available.